This invention relates to a process for the synthesis of 1,8-naphthalimide under atmospheric pressure at a temperature below 100xc2x0 C.
1,8-Naphthalimide is a well known intermediate for pigment and dye synthesis. The reaction of 1,8-naphthalic anhydride to produce 1,8-naphthalimide using a large excess of concentrated aqueous ammonia, performed under high temperature and pressure, is well known in the prior art. Of the major drawbacks of this known reaction process is that it produces a large amount of aqueous ammonia waste water and requires a pressure vessel.
U.S. Pat. No. 3,812,130 describes reacting solid 1,8-naphthalic anhydride with gaseous ammonia to produce 1,8 naphthalimide. The product is isolated directly by evaporating off the water. Although this procedure minimizes waste water, it still requires a pressure vessel and has the disadvantage of not allowing for any water soluble impurities or unreacted starting material to be removed after the reaction. Thus, a potentially impure product is produced.
Other sources of ammonia have been used in the prior art to react with 1 ,8-naphthalic anhydride. For instance, Israeli Patent IL 38852 discloses the reaction of urea with 1,8-naphthalic anhydride in refluxing xylene. This process has the disadvantage of requiring an organic solvent.
U.S. Pat. No. 4,892,950 discloses reacting ammonium sulfate with 1,8-naphthalic anhydride. This process, however, requires multiple neutralization and acid acidification steps.
The Russian Publication by Plakidin, V.L. et al., Zh. Org. Khim 18(9): 1997-8 (1982), reports using formamide as the ammonia source, but the procedure also requires high temperatures and a pressure vessel and produces a yield of only about 84%.
Another approach to the synthesis of 1,8-naphthalimide, is the oxidative ammonolysis of acenaphthene using a vanadium catalyst, as described in several Russian publications (Ergalieva, A. Kh. et al. lzv. Akad. Nauk. KAZ. SSR, Ser. Khim. (3): 35-9 1979; Shalabaev, Sh. B. et al. ibib, 27(4): 44-8, (1977); Sembaev, D. Kh. et al. ibid, 26(6): 42-8 (1976); and Russian patent SU 491631). This approach has the disadvantage of requiring high temperatures of 350-360xc2x0 C.
Thus, according to the prior art, the synthesis of high yield and high purity 1,8-naphthalimide in the absence of organic solvents requires temperatures exceeding 100xc2x0 C. and/or high pressure. This stems from the belief that ammonia or ammonia sources are not very reactive at temperatures below 100xc2x0 C. and/or under pressures lower than atmospheric pressure.
The present invention relates to a high yield process for making a high purity 1,8-naphthalimide in the absence of an organic solvent, at a temperature below 100xc2x0 C., and under a pressure atmospheric pressure while producing a minimal amount of waste water.
Other objects and advantages of the present invention will become apparent from the following description and appended claims.